This disclosure relates generally to image processing techniques. More particularly, but not by way of limitation, it relates to novel techniques for performing “blind” image defringing.
In photography, different artifacts can affect the quality of the edges, i.e., the fringes, of objects in the image. This effect is more noticeable when the edge has high contrast. In repairing such a color “fringe” region, it is often effective to merely diminish the noticeability of the fringe. This can be done through chroma replacement with nearby values, desaturation, and by other means.
A color fringe is an artifact where an edge has a noticeable color in it that doesn't match the two colors on either side of the edge. In some images, this may be manifested in the form of a red-purple fringe on one side of a shape in the image and a blue-green fringe on the other side of the shape, for example.
Photographs have color fringes, usually at bright, high-contrast edges, for various reasons. The most common reasons are these: 1.) chromatic aberration of the lens system used to capture the photograph; 2.) light reflection within the micro lens system resident on the image sensor; and 3.) incorrect demosaicing of small (usually neutral) details in the image.
Usual approaches to color defringing involve chroma blur and chroma median filtering, which are operations that apply to the whole image. One motivation for improving upon these usual approaches is the understanding that, typically, not all pixels of an image display color fringing. Usually, fringing only occurs in high-contrast edges. Mere masking of the effects of the whole-image operations can improve the result, but further improvements are still possible.